(1) Field of the Invention
The present invention provides a method and system utilizing the wavelet transform as a method of improving and optimizing the visual display of image data at the time of viewing, to provide enhanced information analysis capability for disease screening and diagnosis, such as breast cancer. Through the use of an interactive software tool, the user can display both unprocessed and processed enhanced images simultaneously as well as control higher enhanced image iterations to produce better image viewing and therefore better diagnosing capability.
(2) Description of the Prior Art
The historical method of conducting mass screening for certain diseases, such as breast cancer, utilizes traditional analog film mammograms produced from x-rays. Once the mammograms are produced, the films are visually inspected by radiologists to determine if any abnormalities exist. Should a suspicious area be visually perceptible, various follow-on procedures are conducted. This process is subjective and dependent upon the level of expertise and thoroughness of the radiologist and the quality of detail of suspicious features in the film mammogram.
For example, the presence of dense breast tissue can mask subtle abnormal features in the mammogram. Cancer in the early stages may go undetected for some period of time. Detection of cancer during later stages of the disease results in more costly invasive procedures at best and may result in loss of life for severe cases.
With the recent advent of full-field, direct-digital mammography, digital acquisition technology that results in images most closely matching those of standard film screen radiography is becoming the standard method for screening. The advantage of digital mammography currently is that the image can be generated with confidence that technical features and factors will be satisfactory and the imaging will not need to be repeated, thus maximizing efficiency for the facility and minimizing x-ray dose exposure to the patient.
While such advantages are important, the opportunity exists for software tools which allow the radiologist to visually enhance features in digitally acquired images at the time of viewing to yield more information than was ever available with standard film screen radiography. With direct digital acquisition, additional benefits for image optimization can be realized through preprocessing and post-processing of image data. Rather than printing digital images onto film for interpretation by the radiologist, the same images can be available for viewing directly on a monitor.
Various wavelet techniques are used to enhance the visual and quantitative presentation of important image features. The use of wavelet transformation for image enhancement is known in the art of x-ray and ultrasonic imaging. Further the use of multiple image display capability is also known. However, the prior art does not demonstrate a unique system and method which allows a physician or other image reader to acquire raw, unprocessed data and interactively and iteratively perform image processing operations to enhance the image while maintaining the original unprocessed image for reference and comparison.
The present invention features an interactive method to detect, isolate, and visually enhance features in digital images.
The wavelet transform accepts all of or a specific portion of a digitized image, such as a mammogram, as the input image, and using multi-spectral decomposition, produces a mathematical model or algorithm representing the digital image across various frequencies and spatial positions represented by the transform. The resulting coefficient map is processed according to the selected enhancement method. One dimensional, two dimensional and three dimensional signal and image data may be enhanced, as well as segments of the image.
Once the coefficient map has been processed, an inverse transform is performed to reconstruct the image. The original unprocessed image and the enhanced image are displayed at the same time on the computer monitor. Since this is a variable process which is influenced by size and geometry of the features of interest and, in the case of a mammogram, density of breast tissue, the current process has the capability for three separate enhancement techniques as selected by the user.
The algorithms are parameterized and interactive such that several enhanced images may be produced in real time and the physician or the image reader may control tradeoffs among feature contrast enhancement, background tissue contrast reduction and spatial resolution. The system may also be adapted for use with or by an automated detection algorithm.
The present invention is of special utility in the location and enhancement of subtle abnormalities in breast images, to increase the contrast of the features of interest while simultaneously reducing the contrast of surrounding breast tissue. Suspicious features which would have remained hidden by conventional methods can be visualized in a manner that maintains the highest visual spatial resolution possible while still enhancing subtle features of interest to aid the radiologist to visually locate and interpret these suspicious features.